One known arrangement of the internal combustion engine of this type is to have a water temperature sensor mounted on a water outlet to distribute and supply to a radiator, a throttle chamber, a heater core, etc the cooling water after cooling the cylinder head and cylinder block, as disclosed in the following non-patent document 1, for example. In this engine, the water temperature sensor detects a water temperature of the cooling water after cooling the cylinder head and cylinder block, and according to the detected temperature an electric cooling fan is rotated and controlled so as to keep the cooling water in a suitable temperature.
Non-Patent Document 1: Fuji Heavy Industries Ltd. PLEO Maintenance Manual Vol. 1, '98, 10 Page 2–70
In such an internal combustion engine, however, since the water outlet is made in a divergent structure, and has a branched structure, the main stream of the cooling water after cooling flows past the sensor without contacting it, depending on the installation location of the sensor, and therefore, accurate detection is not possible. As a result, the case occurs that the engine can not detect a temperature of the cooling water accurately.